Feldspar-iron-alkali fischertropsch catalyst and its preparation



. are cobalt, iron, nickel and ruthenium which may results a e Obtainedif the iron oxide is fused UNITED STATES PATENT OFFICE IFEILDSPAR, IRONALKALI FISCHER- TROPSCH CATALYST AND ITS PREP- ARATION Alvin H. Friedmanand Jesse N. Moran, Battlesville, kla., assignors to Phillips PetroleumCompany, a corporation of Delaware No Drawing. Application February 10,1947,

1 Serial No. 727,726

1 11 Claims. (0!. 252-459) This invention relates to the synthesis ofhydrodrogen. Another object is to reduce the formacarbons by thereduction of carbon monoxide with tion of wax in such synthesis. Anotherobject is hydrogen. In one aspect it relates to a new and to facilitatecatalyst fluidization in a fluidized novel catalyst for this synthesisand to the method catalyst type of operation. Many other objects ofmaking such a catalyst. s will more fully hereinafter appear.

In the process .of synthesizing hydrocarbons We have now found that itis highly advanwhich is commonly designated the Fischerta ous to employin the synt s s of dr Tropsch synthesis, carbon monoxide andhydrocarbons by the so-called Fischer-Tropsch method gen are reacted atelevated temperatures in the a reduced ground fused mixture of ironoxide presence of a suitable catalyst to yield hydrocarl0 and a mixedsilicate of aluminum and a metal bons of the constitution ranging frommethane sele d fr m the gro p consisting of the alkali to a wax andsmall amounts of oxygenated matea d lkaline earth metals. Our inventionis rial. The catalysts usually used for this synthesis based n h d s v rt at h h y advanta s be promoted with th lkali metal lk l 16 withsubstantial proportions of such a mixed sillearths, or their oxides, orwith thoria or various cute of m n m and an alkali or alkaline earthother promoters and the catalysts may be supmetal, the resulting f dmixt r e be ported on an inert support such as kieselguhr and ground ande ly with hydrogen. to the like, when a, su rt i employed t h beenconvert the iron oxide substantially to elemental the practice todissolve the active catalytic ma- 20 ironterial and the promoters in asuitable liquid The use Of a po such as h j s been medium and to mix theresulting solution with described is particularly d n ag o s in he thesupport whereupon the promoters and active manufacture of an ironcatalyst which is in be catalyst material are precipitated fromtheir'soemployed in the fluidized p c o reducing lution by means of analkaline solution. The carbon monoxide w h y r to make hydroresultingcatalyst is made into pellets or granules oerbons- Without a support sas i employed for the synthesis reaction. Such pallets or granin o da cew h the p esen in e tion; the ules are employed in the form of a fixedbed of finished iron catalyst has a b e y of about catalyst. when afluidized catalyst modifica- 2. How v r by employment of h s ppo s oftion of this synthesis is employed, in which th 80 the presentinvention, the bulk density of the catalyst is used in the form of afreely flowing iron catalyst can be decreased to as low as or powderwhich is readily suspended in the gaseous ev n low hus by usi t ironoxide h material passing through the reaction zone we unequal Weight o fdsp followed h o have found that it is advantageous to use no grinding od P c e suitable for use support, in the sense of an inert diluentmaterial n t e fluid ed p oc ss, a d reduction W Y- upon which isdeposited the active catalytic madrogen, the b ty o the resulting P wterial. In practicing such fluidized operation in catalyst ready for semay be s W as This accordance with the present invention We fuse d c e en de sity 18 o great advanta in that the active promoter material intothe catalyst the lighter catalyst fluidizes more readly in the and grindthe resulting hard mass to a relatively 4o fiu nt synth sis as and l ssw ht of catalyst hard, abrasion-resistant powder ideally suited for isnecessary.

this type of operation.v We may use any natural or synthetic mixed Theprincipal object of the present invention silicate of aluminum and analkali or alkaline is to provide an improved form of catalyst for theearth metal in the practice of the present insynthesis of hydrocarbonsby the reduction of Ven ion. robably e most readily available and carbonmonoxide with hydrogen. Another obmostv economical mixed silicate foruse in the ject is to provide an improved catalyst for such presentinven n is feldspar- As is Well known synthesis when conducted in thefluidized catathe term "feldspar designates a group of relystmodification in which the catalyst in finely lated minerals composed ofmonoclinic and tridivided form is suspended in the flowing gaseous 5clinic silicates of aluminum with alkali or alkareaction mixture.Another object is to provide a line earth metals, commonly potassium,sodium process of making such an improved catalyst. and calcium. Samplesof minerals coming with- Another object is to reduce the formation ofinthe term feldspar are andesine,albite,anorthocarbon in the synthesisof hydrocarbons by the clase, anorthite, labradorite, microcline,orthocatalytic reduction of carbon monoxide with hyclase and oligoclase.However our invention is 3 not restricted to the use of feldspar.Examples of material other than feldspar which may be employed are micassuch as muscovite, lepidolite, and biotite. We may also use mixedsilicates of aluminum and alkali or alkaline earth metals which aredesignated as feldspathoids such as leucite and materials classified aszeolites such as analcite, stilbite. Other materials which may beemployed in practicing the present invention are marialite, petalite,etc. It will be seen that the presence of elements other than aluminumand alkali or alkaline earth metals in the mixed silicate is notprecluded. Examples of such other elements are halogens. For examplelepidolite contains fluorine, marialite contains chlorine. Combinedhydrogen may also be present as a The first step in the manufacture inaccordance with the present invention is to convert the metallic iron toiron oxide. We prefer to do this in such manner that ferroso-ferricoxide, F6304, is obtained. This is best accomplished by burning themetallic iron in oiwgen. Alternatively, natural ferroso-ferric oxide,such as magnetite, may be used as a starting material. This material maybe purified preliminarily, if desired.

The iron oxide is then mixed with a suitable proportion of the mixedsilicate of aluminum and an alkali or alkaline earth metal and theresulting mixture is fused in any suitable manner. If desired themixture may be agitated during the fusion step by a stream of oxygen.For example a jet of oxygen may be directed on or below the surface ofthe mixture undergoing fusion After a uniform fused mixture is obtained,it is allowed to cool to a temperature suitable for grinding and theresulting material is then ground in any suitable manner to a suitablefineness. Where it is to be employed in the fluidized type of reactionit is preferred to grind it to a fineness such that it will pass a65-mesh screen but be substantially completely retained by a 300-meshscreen or even higher. A catalyst of such particle size appears to bemost suitable for use in a fluidized process since it is flne enough sothat it is readily suspended in the gaseous stream or streams cominginto the reactor and yet it is not so flne as to interfere with itsready separation from the eiiluent gases.

The resulting powdered material is then reduced to effect reduction ofthe iron oxide substantially to the form of elemental iron. This is mostconveniently accomplished by means of hydrogen gas at an elevatedtemperature. For example the powdered material may be reduced withhydrogen at 450 to 550 C. for 48 hours. The resulting catalyst is nowready for use.

The proportions ofiron oxide and the mixed silicate employed inaccordance with the present invention may be varied over wide limits.Practical proportions may range from 20 to 75 percentof feldspar basedon the combined weight of iron oxide and mixed silicate. Frequently apreferred proportion is 50 per cent of iron oxide and 50 per cent of themixed silicate.

We have further found that the use of a mixed silicate which containspotassium or sodium or other alkali metal or alkaline earth metal incombination with alumina and silica also acts as an effective promoterfor the synthesis reaction. The alkali metal or alkaline earth metaloxide is present in the mixed silicate in a suitable form to act as apromoter for the iron catalyst. This is particularly the case where thealkali metal or alkaline earth metal oxide and the weakly acidic silicaand alumina are present in simple molecular proportions.

However while the mixed silicate employed in accordance with the presentinvention serves as a promoter because of its content of alkali metal oralkaline earth metal, additional activators such as potassia, potassiumnitrate and the like may be incorporated in the catalysts of the presentinvention. Such incorporation of ex-- traneous promoters may be effectedin any suitable way. i

The catalyst prepared as described above is employed in the synthesis ofhydrocarbons by the reduction of carbon monoxide with hydrogen. Theusual reaction conditions for the synthesis are employed. The reactionconditions used do not form part of the present invention. The synthesisreaction is usually carried out at pressures ranging from atmospheric tomoderately superatmospheric, depending on the composition of productdesired. A preferred range of pressures suitable for general use is from5 to 20 atmospheres. Temperatures ranging from 175 to 325 C. may beemployed. The flow rate is variable depending upon many factors.Increasing contact time results in somewhat lower operating temperaturesand higher yields per pass with less formation of methane. In order toobtain a satisfactory rate of production, suitably rapid flow rates mustbe employed. Space velocities ranging from 1000 to 30,000 cubic feet ofsynthesis gas per hour per cubic foot of catalyst may be employed.

It is preferred to employ the fluidized mode of operation. Suchoperation of the Fischer- Tropsch process is now well known to the artand need not be described in detail. In such operation the flnelydivided catalyst is suspended in the incoming gas stream and theresulting suspension is maintained in the reactor for the desired periodof time. If desired hindered settling may be provided. In the hinderedsettling type of fluidized operation, a dense phase of catalystsuspension in gas is maintained in the lower portion of the reactor. Thegases leaving the hindered settling zone contain only a small amount ofsuspended catalyst in a form resembling smoke and this type ofsuspension prevails in the upper portion of the reactor. The gases arewithdrawn from the top of the'reactor and are treated in any suitablemanner to separate traces of suspended catalyst and to recover thedesired product and recycle stream.

The use of relatively large quantities of the mixed silicate in theformulation of the catalyst of the present invention is highlyadvantageous since it enables the catalyst activity for carbon and waxproduction to be decreased to the point where less carbon and wax areformed as primary products in the reaction, but the catalytic 1 activityfor the synthesis of gasoline range hydrocarbons is still held at a highlevel. We believe that this is due to the alteration in the catalyststructure to make a harder, less porous structure in the finishedcatalyst granule, but we do not wish to be restricted by this theory.

What we have invented and disclosed in this specification is the use asa support and promoter of a natural mineral such as feldspar or of itssynthetically prepared equivalent in the Fischer- Trop sch synthesiswith the advantage, which is especially pronounced when large quantitiesof the mixed silicate of the order of 50 per cent are used, ofdecreasing the density and activity'of acted with synthesis gas composedof two parts of.

hydrogen and one part of carbon monoxide at 150 pounds per square inchgauge and 320 C. using 2500 volumes of synthesis gas per volume ofcatalyst per hour. Four and one-half cc. of liquid product was made perhour, including some wax. After 56 hours the reaction was stopped andcarbon and some wax was found on the' catalyst.

In comparison with this run a sample of the same wire burned in oxygenwas mixed with an equal weight of feldspar and fused in an oxy-hydrogenflame. The bulk density of this powder was 1.8.' After reduction andtreatment at the same conditions as in the previous example the reactionwas observed to yield 6 cc.-of liquid per hour, substantially all ofwhich was in the gasoline range. After 54 hours the reaction wasstopped. There was no wax on the catalyst and no evidence of carbonformation.

It was ground to 65/100 mesh..

with resultant improve- From the foregoing description it will be seenthat many advantages flow from the practice of the present invention. Animportant advantage is that the density of the catalyst is greatlyreduced. Another advantage is that the catalyst activity is decreased sothat less carbon and wax are formed although the activity of thecatalyst for the desired synthesis reactions is maintained at ahighlevel. Another advantage is that the.

support also furnishes a very good promoter for the catalyst. Anotheradvantage is that the supports are cheap and readily available, feldsparfor example being a relatively abundant material in the earth's crust.Another advantage is that the preparation of the catalyst is simple andis easily carried out. Many other advantages will be apparent to thoseskilled in the art.

We claim:

1. As a new catalyst, particularly suited for catalyzing the synthesisof hydrocarbons by the reduction of carbon monoxide with hydrogen, .areduccdparticulate fused mixture of iron oxide and a. mixed silicate ofaluminum and a metal selected from the group consisting of the alkaliand alkaline earth metals, the amount of silicate ranging from 20 to 75weight per cent of the mixture of silicate and iron oxide, and the ironbeing in elemental form.

2. The catalyst of claim 1 in which said mixed silicate is feldspar.

8. The catalyst of claim 2 in which said feldspar and iron oxide are inequal proportions.

4. The process of preparing a catalyst'particularly suited forcatalyzing the synthesis of hydrocarbons by the reduction of carbonmonoxide with hydrogen which comprises fusing iron oxide with a mixedsilicate of aluminum and a metal selected from the group consisting ofthe alkali and alkaline earth metals, cooling and comminuting theresulting mixture, and reducing the resulting material under conditionswhich convert the iron oxide substantially to elemental iron.

5. The process of claim 4 wherein said mixed silicate is employed in anamount ranging from 20 to '75 per cent by weight based on the weight ofsaid iion oxide and said mixed silicate.

6. A process of preparing a catalyst particularly suited for catalyzingthe synthesis of hydrocarbons by the reduction of carbon monoxide withhydrogen which comprises burning metallic iron in oxygen, mixing theresulting oxide with feldspar, fusing the resulting mixture, cooling anddividing the resulting mixture into small aggregates, and reducing theresulting particulate material with hydrogen at an elevated temperatureunder conditions which convert the iron oxide to elemental iron.

7. The process of claim 6 wherein the proportions of the oxidized ironand of the feldspar are approximately equal.

8. The process of preparing a catalyst particularly suited forcatalyzing the synthesis of hydrocarbons by the reduction of carbonmonoxlde with hydrogen which comprises burning metallic iron in oxygen,mixing the resulting ron oxide with about an equal Weight of feldspar,fusing the resulting mixture in an oxy-hydrogen flame, cooling,comminuting the same to a particle size of between about 65-mesh andabout 300-mesh, and reducing the result ng powdered material withhydrogen at a temperature between 450 and 550 C. until the iron in themixture is reduced to elemental iron.

9. As a new catalyst, particularly suited for catalyzing the synthesisof hydrocarbons by the reduct=on of carbon monoxide with hydrogen, a

reduced particulate fused mixture of feldspar and magnetite, the amountof feldspar ranging from 20 to weight percent of the mixture of feldsparand magnetite. and the iron in said magnetite being in elemental form.

10. The process of preparing a composition readl'y reducible to acatalyst containing elemental iron and particularly suited forcatalyzing the synthesis of hydrocarbons by the reduction of carbonmonoxide with hydrogen, whichcomprises fusing iron oxide with a mixedsilicate of aluminum and a metal selected from the group consisting ofalkali and alkaline earth metals, cooling the fused mass, and dividingthe same into small aggregates.

11. A composition which reduces so as to form a catalyst particularlysuited for catalyzing the synthesis of hydrocarbons by the'reduction ofcarbon monoxide with hydrogen and consisting essentially of a fusedrnxture of iron oxide and a mixed silicate of aluminum and a metalselected from the group consisting or the alkal and alkaline earthmetals in which said iron oxide is readily reducible to elemental iron.

ALVIN H. FRIEDMAN. JESSE N. MORAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

'UNITED STATES PATENTS Date

